The present invention relates to a technology to control power from distributed energy resources linking with a power system.
A route and an electric facility to provide commercial power supply from a power supplier such as a power company to individual users (private houses, buildings, factories, and the like) are called a power system. In the usual case, individual users, except some large-scale users, have used only the commercial power supply from the power system.
However, in recent years, popularization of the energy sources with a small load to the environment such as solar photovoltaic power generation, wind power generation, a heat pump, and a fuel cell has been desired. Because these power supplies are installed at individual users, they are called distributed energy resources, as compared with conventional large-scale electric power plants established in concentrated ways at places apart from urban areas.
In the case where a failure occurs in the power system, it is necessary to shut down all the distributed energy resources connected to the power system evenly for work. Accordingly, the distributed energy resource is equipped in advance with an apparatus to prevent islanding operation (JP-A-2007-37354, JP-A-2005-33851). In addition, there has been proposed a method for contributing in maintaining a voltage and a frequency flexibly and simply by improving an inverter apparatus of the power supply assuming an independent power supply system for power supply for an isolated island or power supply for a disaster area (JP-A-2000-341958).